Equipment has been developed to allow for the filling of high-pressure oxygen cylinders in the home. This equipment includes couplings to connect the cylinders to the equipment during filling. Oxygen can be trapped behind the couplings when the cylinders are removed. This trapped oxygen must be overcome to connect another cylinder making it difficult for people with limited strength to operate the equipment. The invention provides a coupling that can, among other things, bleed the trapped oxygen after removing the cylinder.